Variable voltage generator



E. RASMANIS ETAL 3,139,600

June 30, 1964 VARIABLE VOLTAGE GENERATOR Filed Dec. l2, 1960 2 Sheets-Sheet l l 1 I I FIG.I

INVENTORS EGONS RASMANIS BY GERALD J. SELVIN SMN ATTORNEY June E. RASMANIS ET AL VARIABLE VOLTAGE GENERATOR EGONS RASMANIS BY GERALD J. SELVINv www ATTORNEY ration in, and convenient interconnection with, other1 United States Patent O t 3,139,600 p VARIABLE VQLTAGE GENERATOR Egons Rasrnanis, Burlington, and Gerald J. Selvin, Wayland, Mass., assignors to Sylvania Electriclroducts Inc., a corporation of Delaware Filed Dec. 12, 1960, Ser. No. 75,409 11 Claims. (Cl. 2338-32) This invention relates generally to voltage generating devices and more particularly to a variable kHallvoltage generator. n

With the use oi' microelectronic circuitry becoming more common, a need has been developed for a simple, small, reliable, and inexpensive variable voltage source for usel with such circuitry. In the deevlopment of the microelectronics art thus far, it is becoming more and more evident that future electronic circuits will notbe yspecified in terms of the performance of its component quency control in microcircuitry is best achieved by*l means` of voltage variable capacitor diodes, the capacitance of which is controlled by Varying the impressed voltage. This element, then, aiiords (a means for frequency control without requiring access to a rotatable shaft or other device vfor adjusting the frequency. However, for j ythe voltage variable capacitor diode to be practical in a microelectronic circuit, a source ofvariable Voltage of a size comparable to that of the rnicroelectronic circuit with which'it is to be used, and of comparable reliabilityis required. Presently available potentiometers *are lconsiderably 4larger than microelectronic circuit modules, and voltage control is achievedby aA mechanicalwiping contact to vary resistance. LThe mechanical aspects of the potentiometer reduces its reliability, yand hence the reliability of the circuit with which it is used, andthe size kalone limits its usefulnessrin microelectronics.

It is, therefore, an object of the present invention to suitable for inicroelectronic applications.

Patented June 30, 1964 icc ' Still another object of the invention is to provide a variable voltage generator which may be Vreadily controlled externally of an hermetically sealed microelectronic module without disturbing the hermetic seal of the f electronic material which aiords the voltage control.

yThese and other objects-are attained, in accordance with the invention, by the utilization of the Hall effect and a variable magnetic field. The Hall ,etfecn discovered in 1879, has to do with the creation of an electric field in a solid when a current ilows through it in the presence yot a magnetic field. The electric iield created is ymanifested as a voltage, usually referred to as the Hall voltage, the magnitude of which depends on the vector cross-product of the current now, the magnetic iield and other factors. When a sample of semiconductor material is properly oriented in a magnetic field, and current 'is passed through it in a direction perpendicular to the magnetic field, the voltage developed may be expressed VHzkIB sin 0 where k is a material constant, I is the current passing through the sample, E is the llux density of the magnetic field, and 0 is the angle between I and B. In accordance with `the present invention, the iluxdensity of the magnetic field in which the semiconductor'material is placed is varied by a relatively Simple expedient of relative rol tation between "two permanent magnets, thereby to vary the voltage developed across the specimen. By using extremely thin specimens of available semiconductor materials, available magnets, in sizes compatible with microkelectronic circuitry, are capable of producing magnetic provide an improved variable voltage generator of a size( A further object of this invention is to provide a vari-` ,j

able voltage source in which voltage control is obtained by molecular change in a solid state material, so as to' be compatible with circuit elements employed inmcro-k' y electronic circuit modules. n n

Another object ofthe invention is to provide a variable voltage generator vhaving the foregoing characteristics in which the materialatfording the voltage control is herr-` rnetically 'sealed to achieve high reliability. t

Still anotherfobject of the invention is to provide a variable rvoltage generator capable of delivering voltages of a magnitude encountered in ysemiconductor circuitry. Still another` object of the kinvention is 'to provide a variable voltage source comparable in 'size to other elej ments of a microelectronic module to permit its incorpocircuit stages in a niicroelectronic module.

fieldA strengths which will produce yI-Iall voltages having magnitudes usefulfin such circuitry. Since the Voltage control is obtained by variation in the ilux density of the magnetic field, the semiconductor material kmay be hermetically sealedin a chamber separated `from the magnets whereby the magnets may e rotated relative to each other without afiectingthe seal. j

Other objects, features, and advantages` ofv the invention, and akbetter understanding oi its construction andk operation, will become apparent from the following detailed description, taken in conjunction with the accomlpanying drawings, in which:

FIG. 1 is a schematic diagram useful in explainingthe' Hall effect;

FIG. 2 is anv isometric View, partially cut away, of a preferred form ot variable voltage generator embodying the invention; f l

FIG. 3 is an isometric view of the underside ofthe assembly of FIG. 2; f

FIG; 3A is an enlarged fragmentary `View of a portion of FIG. 3;

FIGS. 4A and 4B are diagrammatic illustrations of l the Variable voltage generator of FIG. 2 illustrating how the flux density of the' magnetic iield is controlled;

FIG. 5 is a' diagrammatic cross-sectional view of the voltage generator of FIG. 2 illustrating an alternative construction; and y' V FIG. 6 is an elevation view of a microelectronic circuit module incorporating the present voltage generator.

Briefly reviewing the Hall eiiect on which the present invention is based, if a current is made to flow through FIG.- 2A is a plany view of the underside of the magnet assembly of FIG. 2, with the supporting wafer removed;

a wafer of semiconductor material in a direction parallel to its long dimension, and a magnetic lield is applied in a direction perpendicular to the current flow, a voltage is observed across the sample along the axis normal to both the direction of current liow and the direction of the magnetic field. This is pictorially presented in FIG. 1. The Hall voltage, designated VH, is the result of charge accumulation on the two surfaces of the material. While the magnetic field is building up, a transverse current actually flows in the specimeniand the charges accumulate on the two opposite faces, making one side positive and the other negative. The Hall voltage across a sample of semiconductor material of thickness d and of rectangular cross-section as illustrated, is given by VH d where VH is in volts, I is in amperes, H is in gauss, d is in centimeters, and R is in cm3/Coulomb. rl`he coeffcient l-8 is included to convert electrostatic units to practical units. It is obvious from this equation that if the physical dimension d is decreased, the Hall voltage, for a given magnetic field, will increase, and that the Hall voltage is also proportional to the magnetic `field. Thus, by varying the strength of the magnetic field applied to a semiconductor specimen, it is possible to obtain a variation in the Hall voltage.

In accordance with the invention, the variable magnetic field is produced across a specimen of semiconductor material by a pair of cooperating magnets so shaped that one lits over and substantially surrounds the other and arranged for relative rotation between them. The semiconductor specimen is positioned with respect to the magnets so as to be substantially normal to the lines of magnetic flux. When the magnets are turned to a position where like poles are adjacent, the magnetic field across the specimen is at a maximum, and when one magnet is rotated with respect to another to a position where opposite poles are adjacent, essentially no magnetic field is applied to the specimen. Intermediate positions between these two extremes afford controllable levels of magnetic flux in the specimen.

Referring to FIG. 2 where this concept is shown embodied in a structure suitable for incorporation in a microelectronic module, an inner magnet is shown supported on a thin ceramic wafer 14 having tabs projecting from the edges thereof, one of which is shown at 14a. Wafer element 14 may be of the form shown in co-pending application S.N. 55,238, filed September l2, 1960, by Messrs. John R. Moore, Gerald I. Selvin and Robert E. Stapleton, entitled Microelectronic Circuit Modules. The Wafer is formed of a rigid insulating material such as a high density, high purity alumina, such as No. AD-99, available from the Coors Manufacturing Company, or Al Si Mag No. 652 or No. 614, available from the American Lava Company. The wafer element is shown greatly enlarged inthe drawing, typical dirnensions for the element being 0.5" X 0.5 with a thickness of 8-l2 mils for the module described in the aforesaid application. vWafer 14 may be formed with an equal number of integral tabs projecting from each of the edges of the Wafer in the plane of the wafer, Vso as to correspond with the other wafers of the module described in that application, but may be formed with only four tabs 14a, 14b, 14C and 14d, two extending from each of a pair of opposite edges of the wafer as shown in FIG. 3.

Magnet 10,` preferably formed of Alnico V because of its good temperature stability, is of generally rectangular shape in plan, with a pair of opposite ends curved as shown in FIG. 2A to lie on a circle. In the illustrated embodiment, magnet 10 is secured to the wafer 14, substantially at the center thereof, by fusing or otherwise bonding it to the Wafer element. Magnet 12 is essentially U-shaped in cross-section, the channel therein being of circular shape to fit over and around magnet 10 and to be rotatable with respect thereto. As shown in FIG. 2A, the radius of the opening in magnet 12 is slightly greater than the radius of the curved ends of magnet 10 so as to define a narrow gap 11 between the magnets. To facilitate rotation of magnet 12 relative to magnet 10, the latter is formed with an upstanding shaft 10a, coaxial with the center of the curved surfaces of magnets 10 and 12, which extends through a central opening in magnet 12 and serves as an axis about which magnet 12 may be rotated. A flat wafer spring 13, or equivalent, is fitted between the upper surface of magnet 10 and the under surface of magnet 12 to provide friction between the two magnets to maintain magnet 12 at the position to which it is rotated regardless of shock and vibration. The depth of the channel in magnet 12 is sufficiently greater than the height of magnet 10 to allow room for spring 13 and provide clearance between magnet 12 and the wafer 14. For convenience in adjusting the position of magnet 12, a circular plate 16 having serrations about its periphery is secured to the upper surface of the magnet. Alternatively, the plate may be dispensed with and the outer periphery of magnet 12 formed with integral serrations.

The semiconductor element, or Hall plate, is secured on the other side of the wafer 14 from the magnets in a position such that the lines of magnetic flux produced by the magnets are substantially normal to the flat surface ofthe specimen. That is, the element is positioned such that the lines of flux are substantially parallel to the thickness dimension of the specimen. In the embodiment illustrated in FIGS. 2 and 3, three semiconductor elements 18, 20 and 22 are shown attached to the underside of wafer 14, but a single specimen, two specimens, or even a larger number may be used, depending on the voltage desired. Much the same as with a battery, Hall voltage generators may be connected in series to derive a voltage equal to the sum of the voltages generated by the individual elements, or they may be connected in parallel.

The semiconductor material may be selected from several available elements and compounds which exhibit the Hall effect including germanium, silicon indium arsenide, indium antimonide, gallium antimonide, gallium arsenide, indium phosphide, and diamond. From what has been said earlier, if the specimen is made extremely thin, appreciable voltage can be generated with available permanent magnets of small physical size. The semiconductor specimens being very thin, of the order of 0.1 mil or less, they are necessarily supported on a more rigid structure, such as a slab of insulating material, for example, glass or ceramic.

Suitable supporting slabs are shown at 28, 24 and 26 in FIGS. 2 and 3. Sufliciently thin specimens may be made by mounting the semiconductor material on the support and lapping and polishing the material down to the desired thickness. Preliminary experiments have shown that n-type germanium of approximately 10 ohm centimeter resistivity can readily be polished and etched down to a thickness of less than 0.0005 and that thicknesses of 0.0001" are feasible with germanium. With the latter thickness and an effective magnetic field of approximately 4000 gauss, voltages of about 10 volts are obtainable.

Although a semiconductor specimen is shown supportedY on only one side ofthe slabs 24, V26 and 28 it is within the contemplation of the invention to position a specimen or film-on each side of each slab.

The supporting slabs are secured to the under side of the wafer 14 with their length dimension perpendicular to the lines of flux ,of the field produced by the magnets. The slabs may be secured by firing metallic films onto wafer 14 in the region `where it is desired to attach the supporting slabs, and onto the surface of the slab opposite the semiconductor specimen, and welding this slab to the wafer with a metal L-shaped member 30, best seen in FlGS. 4A and 4B. As shown in FIG. 4A with this mounting the magnetic flux passes through the lm of through printed wiring on the under surface of ceramick wafer element 14. This current may be supplied from a source external and separate from the voltage generator, or may be supplied by a battery mounted on the wafer when' a suitably small battery becomes available. In FIG. 3, the three wafers are yshown connected to supply current thereto in parallel from a source external of the generator. As has been suggested, the current source may be a battery mounted in another y*portion of the module of which the present generator is contemplated as an element, or as a separate component'disposed adjacent the module. The terminals of the voltage source, shown diagramamtically at 33 in FIG. 3,'are connected to tabs 14a and 14d on one edge of the wafer, these tabs being covered with a conductive film or coating. As will be more fully described, the remotely positioned current source is preferably connected to the conductive tabs 14a and 14d by interwiring boards having'tab-receiving slots therein into which the tabs 14a and ldd are inserted. Tab

14a is electrically connected in 'parallel to one end of each of the semiconductor specimens by printed conductor 32 whichis bonded, evaporated, fired on, or otherwise aflixed to ceramic wafer lll, and conductive tab 14d is similarly connected to the other end of the speci-V men by conductor Printed conductors 32 and 34- may be soldered, welded or otherwise secured in tirm electrical contact with currentk supply terminals secured to the end faces of semiconductor specimen Ztl. For

proper operation, a current ow through the specimen of- 1l) and y,rotatable with respect thereto. When magnet 12 is turned to the position where its north and south poles are respectively yadjacent the north and south poles of `magnet 1li, as shown in FIG. 4A, the magnetic ux lines extend through the ceramic wafer 14 and pass through the semiconductor wafer in a direction substantially parallel to the thickness dimension of the specimen. This relative orientation of the magnets also produces maximum iield strength in the vicinity of the specimen.

When the magnet 12 is rotated through 18() degrees to thek position shown in 4B, with opposite poles of the magnets adjacent each other, the lines of linx extend along short pathsv across the lield gaps between the opposite poles with the consequence that no ield is applied to the specimen. l

In this case, no Hall voltage is generated. Intermediate positions of magnet 12, between that shown in FIG. 4A and that shown in FIG. 4B, provide `magnetic llux inten* sities of controllable level. Consequently, with constant current flowing through the specimen, the Hall voltage generated by the specimen is'proportional to the relative orientation of magnets 1t) and 12.

While the specimen is shown in a position perpendicular to thewaier 14 and equidistant the ends of magnet 10, it will be evident that there are other locations and positions or the specimen where the lines of ilux are normal to the specimen. For example, as shown in FIG. 5, Hall plates #ttl and i2 may be supported on slabs 44 and do, respectively, and positioned in a plane parallel to the surfaces oi water 14.k When like poles of the two magnets are adjacent to each other, as shown in FlG. 5, the lines of ilux are substantially normal to the water as shown, and of maximum intensity. posite poles kare adjacent, as will be observed from FlG. 4B, such linx as does pass through the specimen is essentially parallel to the surface ot the specimen with the result that little or no l-lall voltage is generated. At intermediate relative positions of the two magnets, the linx is at different levels of intensity resulting in a variation in i the magnitude of the generatedl-lall voltage.k

` Referring again to FlG. 2, to insure stability of the extremely thin films ot semiconductor material they are preferably hermetically sealed from their surrounding environment. To this end, the semiconductor specimens and their supporting slabs are cupashaped cover or hat Sil placed over the Specimens, and sealed fat its periphery to wafer i4. lt is to be noted ythat'the conductorsiZ, 34, 36 and i2 k(FlG. 3) must be terminals may-be' evaporated to the 'semiconductor mate- 1 rial, or thermo-compression bonded, or may be pressure contacts, or probes, rmly contacting the film ZZat the conductive tab 1de projecting from the edge of wafer14 opposite that to which the currentsource is connected.

If a single semiconductor specimen is used the .terminal 38 at its upper edge may be connectedy with a flexible the terminal on the upper edge of the iirst is connected to the lower terminal of the second (not shown), the upper terminal of the second is connected to the-lower terminal of the third, and iinally, the upper terminal of y 12 about magnet itl on'the other side of the wafer does not disturb the hermetic seal in anyway. Consequently,

the third is connected to printed conductor 4,2' and thence to conductive tab 11th. Thus, the Hall voltage, VH, is

` produced across tabs 14C and ldb'andimay be applied tor circuitry on other wafers inthemodule via a second interwiring board having slots for receiving tabs 14C and `14b and wiring thereon forselective connection of thesey tabs to circuitry on other wafer elements. y

brought through a perimetral seal to make connection with their corresponding conductive tabs. The cover may be formed of glass and joined to the ceramic wafer by a glass-to-glasscerarnic seal, or may be made of metal and joined to the wafer by a metalic-metal-toglassto-ce ramic seal. In either case, provision is made for bringing conductors on the wafer through thehermetic seal for e'onnection'to the conductive tabs. During the sealing k process, an inert atmosphere may be introduced inside the cover'should this be necessary for stability of the semi-k conductor specimens. Suitabley seals for this purpose, and methods for fabricating the same, are described in detail in co-pending application SN. 55,238, filed Septem ber-l2, 1960, by Messrs. LR. Moore, G. J. Selvin and R. E. Stapleton, entitled Microelectronic Circuit Modulesj? and assigned'to the assignee of the present application. With the specimens thus sealed tothe underside of water 141, it will be apparent that rotation of magnet y manual adjustment of the voltage source is possible from a' point externally of the generator without expensive or troublesome sealing of-shafts or the like'.

VVthile the disclosed voltage generator has general ap- .plicability, itis particularly useful in micro-miniaturized -modules of the type'disclosed in co-pending application S.l"-T.-/96,577, led March 2., 1959;, by Gerald'LSelvin, now Patent No. 2,999,686, and assigned to the assignee However, when op` hermetically sealed by a *y of the present application, and in modules of the type disclosed in the aforementioned co-pending application S.N. 55,238. The modules described in these applications comprise a plurality of thin wafers, preferably formed of ceramic material, on which circuit elements or subcircuits are applied, as by printing or evaporation techniques, or by physical attachment. The wafers are all of the same size and shape, preferably square, and each is provided on each of its edges with the same number of integral tabs. The terminals of the circuit elements on a wafer are conductively connected to selected ones of the tabs on the wafer, the selected tabs being rendered conducting, as by coating with a suitable metal. A group of wafers, having the necessary circuit elements thereon to form, when connected, a required circuit, are stacked one on the other with the active conductive tabs innerconnected by an insulating interwiring board, also formed of ceramic, which engages and makes electrical contact with the projecting tabs. The interwiring board is formed with a plurality of slots spaced to receive the tabs extending from one edge of the stack, with selected slots interconnected with printed wiring to interconnect the active tabs on the wafers. Depending upon the nature of the circuit constituted by the module, one or more up to four separate interwiring boards may be required to make the necessary interelement connections. Thus the stacked wafers and their associated interwiring boards provide a rugged, rigid module of high component density.

Referring to FIG. 6, the appropriate wafers to constitute a circuit are stacked into a module with the tabs on the wafers projecting into slots formed in the interwiring boards, two of which are shown at 52 and 54. The tabreceiv-ing slots in the boards 52 and 54 are accurately spaced to support one wafer substantially in contact with the surface of the hat on the immediately adjacent wafer. In order to have access externally of the module to permit rotation of magnet l2, the wafer on which the generator is supported preferably constitutes on end closure of the module, and it may be desirable, as protection for the hat on the lower Wafer to provide an end closure consisting of a blank wafer element 56. The interwiring boards 52 and 54 may be of the construction described in the aforementioned Selvin application S.N. 796,577. rThe boards are formed of the same material as the wafers, with those slots to which connection is to be made to an active tab surrounded by conductive material, and the slots interconnected by printed wiring red or otherwise affixed to the surface of the boards. Preferably four interwiring boards are used so as to completely enclose the wafers, but a sufficiently rigid module can be fabricated with two interwiring boards. It will be understood that ladditional wafers would be stacked in the region between end closure 56 and the generator; these have been omitted for purposes of clarity.

From the foregoing it is apparent that applicants have provided a Variable voltage generator wherein the sensitive electronic material is hermetically sealed, with the necessary conductors connected therewith brought through the seal for external connection, and with adjustment possible by externally accessible means without disturbing the seal. The generator is extremely small, and may be conveniently assembled with additional wafer elements carrying electronic components or sub-systems to produce a microelectronic module.

While there has been described and shown that are now considered to be preferred embodiments of the invention, various modifications may be made without departing from the true spirit thereof. Other semiconductor materials than those enumerated might be used without departing from the spirit of the invention, and, of course, magnet 12 may be rigidly positioned on wafer 14 and magnet 10 rotated with respect thereto -to obtain a magnetic linx of variable intensity. Also, as has been suggested, should a sufficiently small battery capable of supplying the current requirements of the Hall generator become available,

it is contemplated that it might be positioned within the sealing hat Sil with connections made directly from the terminals of the battery to the semiconductor specimens, thus eliminating the need for the printed conductors 32 and 34 connected to conductive tabs Ma and Mb. Therefore, it is intended that the invention not be limited by what is shown and described, except as such limitations occur in the appended claims.

What is claimed is:

l. A variable voltage generator comprising, in combination, first and second permanent magnets, said second magnet substantially surrounding said first magnet and rotatable with respect thereto to provide a magnetic field of maximum intensity when like poles of said first and second magnets are adjacent and of minimum intensity when opposite poles of said first and second magnets are adjacent, a semiconductor wafer disposed in said magnetic field substantially normal to the lines of magnetic flux when said magnetic field is of maximum intensity and having current supply terminals and Hall electrodes to provide an output voltage proportional to the product of the current in said semiconductor and the intensity of said magnetic field, and means for rotating said second magnet relative to said first magnet for varying the intensity of said magnetic eld.

2. A variable voltage generator comprising, in combination, a supporting plate formed of non-magnetic material, first and second permanent magnets supported on one surface of said plate, said second magnet substantially surrounding said `first magnet and axially rotatable with respect thereto to provide a magnetic field of maximum intensity when like poles of said first and second magnets are adjacent and of minimum intensity when opposite poles of said first and second magnets are adjacent, a semiconductor element secured to the other surface of said plate and disposed in said magnetic field substantially normal to the lines of magnetic flux when said Imagnetic held is of maximum intensity and having current supply terminals and Hall electrodes to provide an output voltage proportional to the product of the current in said semiconductor element and the intensity of said magnetic field, and means for rotating said magnets relative to each other for varying the intensity of said magnetic field.

3. A variable voltage generator comprising, in combination, a fiat supporting plate formed of nonmagnetic material, a first permanent magnet secured to one surface of said support plate, a second permanent magnet of U- shaped cross-section substantially surrounding said first magnet and rotatable with respect thereto to provide a magnetic field of maximum intensity when like poles of said first and second magnets are adjacent and of minimum intensity when opposite poles of said first and second magnets are adjacent, a semiconductor element secured to the other surface of said support plate and oriented in said magnetic field substantially normal to the line of magnetic flux when said magnetic field is of maximum intensity and having current supply terminals and Hall electrodes to provide an output voltage proportional to the product of the current in said semiconductor element and the intensity of said magnetic fields, an enclosure around said semiconductor element hermetically sealed to said support plate, and means for rotating said second magnet relative to said first magnet for varying the intensity of said'magnetic field. 4

4. A Hall voltage generator for producing a variable output Voltage comprising, in combination, a fiat support member formed of non-magnetic material, a first permanent bar magnet having curved ends secured to one surface of said support member, a second permanent magnet of U-shaped cross-section positioned over and substantially surrounding said first magnet and defining therewith a pair of field gaps, the sides of the channel in said second magnet being curved similarly to the ends of said first magnet to be rotatable with respect to said intensity and having current supply terminalsv and Hall t electrodes to provide an output voltage proportional to the product of the currenty in said' semiconductor element and the intensity of said magnetic field, a cup-shaped enclosure of non-magnetic material positioned over said semiconductor element and hermetically sealed to said other surface of said support member, and means accesst ible from outside the generator for rotatingsaid secondy magnet relativeito said first magnet for varying the intensity of said magnetic field. e i

5. A variable Hall voltage generator for use in a microelectronic circuit module comprising, in combination, a cermaic wafer having tabsA projecting from at least one edge thereof,`a first permanent magnet secured to one surface of said wafer, a second permanent magnet of U-shaped cross-section positioned over and substantially surrounding said yfirst magnet and defining there-v with a pair kof field gaps, said second magnet being 'rotatable with respect tosaidk first magnet to provide a v magnetic field between said gaps of maximum intensity.

when like poles of said first and second magnets are adjacent and of minimum intensity when opposite poles of said first and second magnets are adjacent, a semiconductor element secured tothe other surface of said wafer and disposed in said magnetic field substantially normal to the lines of magnetic flux when said magnetic field is of maximum intensity and having current supply yterminals and Hall electrodes to provide an output voltage proportional to the product of the current in said elementandrthe intensity of' saidmagnetic field, electrical conductors secured to s-aid other surface of said wafer connecting said Hall electrodes to a pair of said tabs, a

f cup-shaped enclosure of non-magnetic material positioned over said semiconductor element and said conductors and hermetically sealed to said wafer, and means accessible from outside the generator for rotating said second v magnet relative to said first magnet for varying the intensity of said magnetic field. v f

6. A variable Hall voltage generator for use in a microelectronic circuit module comprising, in combination, a

ceramic wafer having tabs projecting from at least onek edge thereof, a first permanent bar magnet having curved ends lying on a first circle secured to one surface ofy said wafer, a second permanent magnet of U-shaped crosssection, the sides of the channel in said second magnet lying on a circle slightly larger than said first circle, said second magnet being positioned over andk substantially surrounding said first magnet and definingv therewith a pair of field gaps, said second magnet being axially rotatable with respect to y'said first magnet to provide a 10 f means accessible from outside said ygenerator for rotating said second magnet relative to said first magnet for varying the intensity of said magnetic field.

7. yA variable volt-age generator comprising, in combination, first and second permanent magnets, said second magnet substantially surrounding said first magnet and rotatable with respect thereto to provide a magnetic field of maximum intensity when like poles of said first and second magnets are adjacent and of minimum intensity when opposite poles of said first and second magnets are adjacent, a semiconductor wafer disposed 1n said magnetic field substantially normal to the lines of magnetic flux when said magnetic field is of maximum intensity and having current supply terminals and Hall electrodes to provide an output voltage proportional to the product of the current in said semiconductor andthe intensity of said magnetic field, and means for rotating said magnets relativerto each other for varying the intensity of said magnetic field. c

8. A variable voltage generator comprising, in combination, first and second permanent magnets, said second magnet lsubstantially surrounding said first magnet and rotatable with respect thereto to provide a magnetic field of maximum intensity when like poles of said first f and second magnets are adjacent and at minimum intensity ywhen opposite poles of said first and second magnets are adjacent, asemiconductor wafer disposed in said magnetic field substantially normal to the-lines of magnetic flux when said magnetic field is of kmaximum intensity and having current supply terminals and Hall electrodes to provide an output yvoltage proportional to the product of the current in said semiconductor and the y intensity of said magnetic field, and means for adjust- VVing the polar position of said magnetsrelative to each other for varying the intensity of said magnetic field.

9. A variable voltagegenerator comprising, in combination, first and second permanent magnetssaid second magnet substantially surrounding said first magnet and rotatable with respect thereto to provide a magnetic 'field of maximum intensity when like poles of said first and second magnets are adjacent and of minimum intensity when'opposite poles of said first and second magnets are adjacent, a semiconductor wafer disposed in said magnetic field substantially normal to the lines-of magnetic fluxL when said magnetic field is of maximum intensityk and having current supply terminals and Hall electrodes to provide anoutput voltage proportional to the .product of the current in said semiconductor and the intensity f of said magnetic field, and means accessible from outside the generator for rotating said magnets relative to each y lotherfor varying the intensity of said magnetic field.

10. A variable voltage generator comprising, in combination, a supporting plate formed of non-magnetic material, first and second permanent magnets-supported on one surface of said plate, said second magnet substantially surrounding said first magnety and axially rotatable magnetic field between said gaps of maximum intensityl i when like poles of said first and `second magnets are adjacent and of minimumintensity when opposite poles of said first and secondk magnets are adjacent, a thin film of semiconductorimaterial supported on the other surface of said wafer and disposed in said magnetic field substantially normal to the lines of magnetic flux when said magnetic field is of maximum intensity and having current 6,5, current supply terminals and Hall electrodes to provide Vwith respect thereto to provide a magnetic field of maximum intensity when like poles ofk said first and second magnetsfare adjacent and of minimum intensity whenv opposite poles yof said first and second magnets are adjacent, a semiconductor element secured to the other surface of said plate and disposed iii said magnetic field supply terminals and Hall electrodes to provide an output .y

film andthe intensity of said'jmagnetic field, electrical conductors secured to said other surfaceof said 'wafer e connecting said Hall electrodes to a vpair of said tabs, a cup-shaped enclosure of non-magnetic material posivoltage proportional to the product of the current in said tioned lover said film of semiconductor material and said y `V conductors and hermetically sealed to said wafer, and

substantially normal to the lines of ymagnetic flux when said magnetic field is of maximum intensity and having an output voltage proportional to the product of the current in said semiconductor element and the intensity of said magnetic field,` and means accessible fromoutside the generator for adjusting the polarpositioii of said magthe intensity of 3,139,600 11 12 one fiat surface of said plate and arranged to provide a semiconductor element and the intensity of said magnetic magnetic ield the intensity of which may be varied upon eld. adjustment of the positions of said magnets relative to each other, and a semiconductor element secured to the References Cited m the me of this Patent other at surface of said plate and disposed in said 5 UNITED STATES PATENTS magnetic field substantially normal to the lines of mag- 2,512,325 Hansen June 20, 195() netic ux when said magnetic eld is of maximum iu- 2,535,805 Hansen jan, 2I 1951 tensity, said semiconductor element having current supply 2,906,945 Weiss Sept, 29, 1959 electrodes and Hall electrodes to provide an output volt- 2,945,993 Kuhrt July 19, 1960 age proportional to the product of the current in said 10 3,077,548 Moresseeet al Feb. 12, 1963 

1. A VARIABLE VOLTAGE GENERATOR COMPRISING, IN COMBINATION, FIRST AND SECOND PERMANENT MAGNETS, SAID SECOND MAGNET SUBSTANTIALLY SURROUNDING SAID FIRST MAGNET AND ROTATABLE WITH RESPECT THERETO TO PROVIDE A MAGNETIC FIELD OF MAXIMUM INTENSITY WHEN LIKE POLES OF SAID FIRST AND SECOND MAGNETS ARE ADJACENT AND OF MINIMUM INTENSITY WHEN OPPOSITE POLES OF SAID FIRST AND SECOND MAGNETS ARE ADJACENT, A SEMICONDUCTOR WAFER DISPOSED IN SAID MAGNETIC FIELD SUBSTANTIALLY NORMAL TO THE LINES OF MAGNETIC FLUX WHEN SAID MAGNETIC FIELD IS OF MAXIMUM INTENSITY AND HAVING CURRENT SUPPLY TERMINALS AND HALL ELECTRODES TO PROVIDE AN OUTPUT VOLTAGE PROPORTIONAL TO THE PRODUCT OF THE CURRENT IN SAID SEMICONDUCTOR AND THE INTENSITY OF SAID MAGNETIC FIELD, AND MEANS FOR ROTATING SAID SECOND MAGNET RELATIVE TO SAID FIRST MAGNET FOR VARYING THE INTENSITY OF SAID MAGNETIC FIELD. 